Hybrid, Maturity, and Cutting Height Interactions on Corn Forage Yield and Quality

Corn (Zea mays L.) hybrids may show different silage quality responses to harvest date and cutting height because hybrids differ in neutral detergent fiber (NDF) digestibility. A brown midrib, leafy, and dual‐purpose hybrid were harvested at early [≈280 g kg−1 dry matter (DM) content], medium (≈350 g kg−1), and late (≈420 g kg−1) harvest dates at 15‐, 30‐, and 46‐cm cutting heights in 2001 and 2002 to determine optimum harvest management for each hybrid type. Most forage quality characteristics had hybrid × harvest date interactions as indicated by the 73 g kg−1 decrease in NDF digestibility of the brown midrib compared with 20 g kg−1 decreases of the other hybrids between the early and late harvest date. Milk per megagram, a forage quality index, declined (1523, 1487, and 1417 kg Mg−1), but DM yields increased (13.2, 13.6, and 14.1 Mg ha−1), so calculated milk yields were similar (20333, 20200, and 20233 kg ha−1) at early, medium, and late harvest dates, respectively, suggesting a broad optimum DM content for harvest. The sharp decline in NDF digestibility, however, raises concern about harvesting the brown midrib hybrid above 350 g kg−1 DM content. Calculated milk yield had a hybrid × cutting height interaction, as indicated by no change in the leafy hybrid and a 13% decrease in the brown midrib hybrid as cutting height increased from 15 to 46 cm. This suggests that an increase in cutting height may be a good management practice for the leafy hybrid but not for the brown midrib hybrid.